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lineset size

been posting a lot lately, thanks for all the help.. lineset question.. 18 seer 2 stage Goodman HP, 3 ton, with matching cased coil. My installer says the lines coming out of the coil and HP are 7/8". I downloaded the manual and there is a chart that says 3/4" lines are fine for a 20 ft run or less, my run will be 14 feet tops. The installer does not want to use the old lines, he wants to run new ones to be completely safe. I think this is great. He wants to use 7/8". That is fine with me, except for what the manual says.. so my question is does it matter if the lines are possibly too big? Thanks, Mike.

probably not in this instance. Without m/s#.... usually the valves are sized for the minimum line set size. The line set may need to be increased if the line set run is excessive. In some cases the line saet may be smaller than the valve (as you indicated). too large of lines can be an issue but will most likely not be in this instance.

The furnace is the GMVM96 80K, fully communicating with the communicating stat. I suppose my problem is that I read too much, but I like to think I do my homework so I don't get taken advantage of. I am being gentle with my installer because I know the last thing any of you like is a homeowner looking over your shoulder! That said, the run would be 12 - 14 feet with a couple long-sweep or formed-into-the-line elbows, plus the slight "s" that will happen between the house wall and the HP. Standing on my basement floor puts my nose at outside ground level, so I suppse the drain pan of the evap is maybe 3 feel below ground level or so? My concern is not so much that I don't get absolute peak performace, althought that would be nice.. My concern is a major performance change or a system that can't get set up (charged) correctly for both heat and cool or some other problems.. Based on the number of elbows and the run length and from what I've read on this site over the years I have to think my installer wants to use the 7/8" for his convenience for some reason.. The current system is a 3 ton also and was a 3/4" suction, and worked great. Thanks!

You or the unit will notice absolutely no difference either way. I would use 3/4. If he wants to use 7/8, let him. The only thing I would be skeptical about is if he wants to use 7/8 because of the valve size. If that's the case, it's a good indication he does not know the specs of the unit he's installing. The ONLY reason that valve is 7/8 is for very long runs/numerous bends and/or elbows. If condensing unit is above coil a trap in suction line may be necessary.

Line set size is critical. ....Not in this caseYour contractor should check with Goodman tech support to run a piping chart on the system with lineset size, length, vertical lift, and elbows. The install guide does call for a 3/4" l.s. your elbows also are equivalent to feet. Also what furnace are you putting this system on. The furnace plays a factor in your seer rating. When we do a system match for a customer the final seer rating will be listed by the manufacturer and AHRI website. I would check these to make sure you are getting what you want.The heatpump that you are looking at is communicating I hope the furnace is a matching communicating furnace with a communicating controller. I could not find the seer rating for the match up provided with out a furnace. If the furnace is not a type of variable speed or ecm then I doubt you will achieve a 15 seer match.... A properly flushed line set is okay, but if your contractor wants to replace it then I would go that way just in case he doesn't know how to properly flush it.........I never flush when replacement is possible. good luck

I saw in the manual where it talks about a trap.. The lines will rise about a foot from the HP to where it enters the house, where it will stay at that level (even height with the "ceiling" of the basement) then turn and drop vertically to the evap then turn again into the evap. I am envisioning 3 long sweep elbows, plus the turn directly into the evap, plus that "s" outside as it rises up to enter the house, like the current system. 2 of the long sweep elbows could be eliminated if the line runs on an angle relative to the floor joists, but that will not look too professional. Do you guys hate guys like me when you do an install?

I saw in the manual where it talks about a trap.. The lines will rise about a foot from the HP to where it enters the house, where it will stay at that level (even height with the "ceiling" of the basement) then turn and drop vertically to the evap then turn again into the evap. I am envisioning 3 long sweep elbows, plus the turn directly into the evap, plus that "s" outside as it rises up to enter the house, like the current system. 2 of the long sweep elbows could be eliminated if the line runs on an angle relative to the floor joists, but that will not look too professional. Do you guys hate guys like me when you do an install?

You are over-thinking this. Either size will be fine in this instance.

I absolutely LOVE the honesty.. I do leave people alone when they work, but I politely ask questions, and even ask permission to ask questions, and I think they are intelligent questions... so maybe it safeguards me against getting taken advantage of. Of course a trustworthy tech never needs to be questioned.. but from a homeowner's point of view, without some information, who do we trust? Plus I have found that if a problem can be described correctly.... that can really help in the diagnosis.. Mike.

I was being facetious with the "and, yes."
I don't mind customers watching or asking questions while I work. In fact I like it when my customers have been educated as to how their equipment works as I think they will then know what to expect and how to use it properly. But don't expect them to question my technical skills or imply that I'm not doing the job properly. The way a question is asked can make the difference between a desire to know something and an implied criticism.